Congratulations!
I am glad to hear your mum is there for you...sounds like you really need the support.
Maybe your bf just needs some time to get used to the idea of being a dad...it can be daunting.
I fell pregnant at 20 also...my BF was a little scared for a while but quickly fell in love with my growing bump and with our daughter when she was born. We didn't have much but we got through with buying 2nd hand and scouring op shops (no ebay back then :LOL
She is now a beautiful, happy, healthy and smart 16 year old